The present invention relates to a technical field of a packet forwarding apparatus having the function to protect traffic in a packet forwarding network.
A high availability technology has been developed for realizing continuation of communication in the event that nodes constituting a network and their physical links become faulty. This type of technique is exemplified by a fast reroute technique of preventing communication interruption in an MPLS (Multi Protocol Label Switching) network. And also, IEEE Internet Draft draft-ietf-mpls-rsvp-lsp-fastreroute-07.txt “Fast Reroute Extensions to RSVP-TE for LSP Tunnels” (RFC 4090), May 2005 (Document 1) describes a one-to-one backup system and a facility backup system, as a system for protecting traffic flowing through an LSP (Label Switching Path) (called a protected LSP) representing a path. In the one-to-one backup system, a single backup LSP is set in association with the protected LSP and in the facility backup system, a single backup LSP is set in association with a plurality of protected LSP's. In the event that a failure takes place in either a node or a physical link by way of which the protected LSP runs, traffic flowing in this LSP is detoured to the backup LSP to thereby materialize communication continuation in the event of the occurrence of the failure.
As another example of the high availability technology, one may refer to a link aggregation technology described in, for example, IEEE802.3ad (http://www.itworld.com/Net/1750/NWW001113tech/pfindex.html), Nov. 13, 2000 (Document 2). In the above technology, a plurality of physical links are treated as a single logical link and a frame is distributed to the plural physical links to make communication. Even when one of the physical links of the logical link becomes faulty, at least one physical link remains sound and communication between switches interconnected by the logical link can be prevented from being interrupted. Accordingly, by interconnecting the switches by the logical link of link aggregation, communication continuation in the event of occurrence of a failure in one physical link can be assured.